On 16/05/2012 20:02, Peter Bigot wrote:
> On Wed, May 16, 2012 at 10:14 AM, Adam Ford<adam.f...@braemarinc.com> wrote:
>> I'm sorry for bugging people, and I have Googled this question, but the
>> answers I'm finding are really old and I know there are updates to
>> mspgcc since most of the answers were posted....
>>
>> I am trying to port 3 different programs from IAR to MSPGCC for work.
>> I'm using the latest released version, but 2 of the 3 won't fit even
>> when compiling using optimizations: -mmcu=$(MCU) -g -Os -Wall
>> -fdata-sections -ffunction-sections and linked with --no-keep-memory
>> -Wl,-gc-sections
>>
>> Does anyone have any ideas how I can further optimize the compiler
>> (other than rewriting - which I've been trying to do)?
>
> The biggest low-hanging fruit I've found is to avoid printf(3c), which
> adds about 2 kB. If you can't avoid it, you can get a few hundred
> bytes back by building an msp430-libc that doesn't support printing
> 64-bit integers. Look at the README at the top level of msp430-libc
> and invoke configure appropriately.
>
> Beyond that rather unhelpful suggestion, no, there are no magic flags
> that I know of.
>
> Peter
>
Is floating point code linked in somewhere? I haven't worked much with
msp430-gcc for a while, and I seldom use printf(), but very often
unexpected large code size can be traced to including floating point
support by mistake.
Other things to look for in the map file are if you've accidentally
pulled in other large chunks of the C library. Sometimes innocent
looking library functions end up forcing in malloc() and friends, or
exit(), or other bits and pieces. Adding a stub such as "void
exit(void) {}" in the C code can sometimes eliminate this sort of thing.
As for "magic flags", does link-time optimisation work for msp430-gcc?
If not, then maybe "-combine -fwhole-program" could help?
mvh.,
David
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